The present invention relates to a process for the synthesis of aromatic ether polymers which contain azo groups along the polymer backbone and to the polymers produced by this process.
Aromatic polyethers are a general class of engineering polymers which contain aromatic rings linked by oxygen atoms exclusively, or oxygen atoms in combination with other groups such as sulfur, sulfone, ketone, alkylene, or imide. More specifically, aromatic polyether sulfones contain both ether and sulfone linkages. Commercially available polyether sulfones are amorphous materials which have very high glass transition temperatures (typically well over 200.degree. C.). Similarly, aromatic polyether ketones consist of aromatic rings linked by ether and ketone groups. Aromatic polyether ketones are high melting, semi-crystalline polymers which exhibit excellent environmental stability, and are commercially available. Typical aromatic polyethers known in the art are described in U.S. Pat. Nos. 4,105,636 and 4,786,694.
Recently, there has been interest in incorporating chromophoric groups into polymer backbones. Polyamides and polyesters containing azo chromophones have been synthesized. See, e.g., Hall et al, Macromolecules. 1987, volume 20, pages 2041-2044; and Bualek et al, Makromol. Chem. 1988, volume 189, pages 797-804. A number of potential applications have stimulated interest in azo-containing polymers. Since the azo linkage perpetuates the persistence direction of the backbone, azo residues have been used as mesogens in liquid crystalline polymers (note the Hall et al reference noted above). In addition, azo units absorb visible light, so that azo-containing polymers have been investigated as possible high grade pigments. See, e.g., Riordan et al, POLYMER. 1979, 20 196. In addition, diphenylazo groups undergo a reversible trans-cis isomerism. Thus, azo-containing polymers are potential photo-responsive materials.
U.S. Pat. Nos. 4,108,837 and 4,175,175 describe a variety of aromatic polyethers prepared by reacting dihalobenzenoids with dihydric phenols (or the double alkali metal salts thereof). Among the dihalobenzenoids described are those containing an azo group (note Examples 31, 32 and 33 of both patents).